System and method for stabilizing a wireless monitoring network

ABSTRACT

Stabilization of a wireless information collection system for dispenser usage compliance in a facility is provided. This system and method enable network stabilization by providing a network “heartbeat.” The network stabilization operates independently from information collection. Therefore, the system and method are able to improve the reliability of wireless information collection systems where the frequency of data collection is not steady.

FIELD OF THE INVENTION

This invention relates to a system and method for wirelessly monitoringdispenser usage in a facility and in particular to stabilizing awireless network for monitoring the dispenser usage.

BACKGROUND OF THE INVENTION

The spread of healthcare acquired infections also known as HAI's hasbeen an ever increasing challenge in health care facilities. HAI'sinclude the transmission of bacteria, viruses and other disease-causingmicro-organisms from various sources such as a patient or environmentalsurfaces to another patient or surface via the hands of healthcareworkers which results in an infection of a patient that was previouslynot infected. These problems have been more apparent in recent yearswith the SARS (severe acute respiratory syndrome) outbreak and theinfluenza A virus H1N1 pandemic. As well, health care facilities havebattled MRSA (methicillin-resistant staphylococcus aureus) and VRSA(vancomycin-resistant staphylococcus aureus) and other drug resistantmicro-organisms for many years. Accordingly, there is a need to ensurethat health care professionals comply with hand hygiene best practices.Hand hygiene can be accomplished using liquids such as a sanitizingproduct which does not require water for rinsing off or alternatively itcan be accomplished using a soap and water.

As well there are other types of liquids that can be dispensed such assun screen. The use of the sun screen may need a similar system andmethod of monitoring, tracking and reporting. For example such a methodcould be very important in schools in Australia where the incidences ofskin cancer are very high.

A need exists for a system and method to reliably monitor, track andreport dispenser usage. Such a system should be low-cost, stable andreliable. ZigBee is a low-power, wireless network standard that mayoffer reliability. However, ZigBee requires network coordinators alongwith routers to establish the network. This additional level of hardwareadds both complexity and cost to a system. Therefore, there is the needfor a reliable routing protocol for a wireless network that is tailoredto improving the stability for low data flow without the use of networkcoordinators.

SUMMARY OF THE INVENTION

A wireless information collection system for dispenser usage compliancewithin a group of interest in a facility is provided. The informationcollected may include the type of product in the dispenser. The type ofproduct could be one of hand soap, sanitizer, lotion, cream, sunscreenand body wash.

The group of interest may be one of a medical unit, a surgical unit, acritical care unit, an intensive care unit, an emergency care unit, apediatric unit, an emergency unit, an outpatient unit, a specialty careunit, a dermatology unit, an endocrinology unit, a gastroenterologyunit, an internal medicine unit, an oncology unit, a neurology unit, anorthopedic unit, an ophthalmic unit, an ear nose and throat unit, aneonatal unit, an obstetrics and gynecology unit, a cardiac unit, apsychiatric unit, a post-operative recovery unit, a radiology unit, aplastic surgery unit and an urology unit. The group may also be one of abed, a room, a ward, a unit, a floor, a facility and a hospital group.

The facility may be one of a health care facility, a food processingfacility, a food service facility, an educational facility and amanufacturing facility. Alternatively, the facility type may be one of ateaching hospital, a non-teaching hospital, a long term care facility,rehabilitation facility, a free standing surgical center, a health careprofessional office, a dental office, a veterinarian facility and acommunity care facility.

The wireless information collection system may comprise dispensers,hubs, and at least one gateway. Each hub may receive data from up to10,000 dispensers and the distance between each dispenser and itsassociated hub may be up to one mile. The wireless informationcollection system may communicate in one or more of the industrial,scientific and medical (ISM) radio bands. ISM radio bands include, forexample, 400-450 MHz, 850-950 MHz, and 2.4-2.5 GHz. Transmission powermay be 1 watt or less.

The wireless information collection system may comprise an ad-hocwireless network to allow for the installation and removal ofdispensers. To ensure that infrequent data messages are passed reliably,a system and method is required maintain active connections independentof data flow.

Further features of the invention will be described or will becomeapparent in the course of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example only, withreference to the accompanying drawings, in which:

FIG. 1 is a diagram showing a wireless information collection system inaccordance with the present invention;

FIG. 2 is a diagram showing an active hub in accordance with the presentinvention;

FIG. 3 is a diagram showing a gateway in accordance with the presentinvention;

FIG. 4 is a diagram showing a receiving hub in accordance with thepresent invention;

FIG. 5 is flow chart showing a method for stabilizing a wireless networkin accordance with the present invention; and

FIG. 6 is sequence diagram showing a method for stabilizing a wirelessnetwork in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Measuring healthcare worker adherence to hand hygiene complianceguidelines is not a simple matter. There are no proven standards orbenchmarks that may be used. However there is a very clear need tomonitor and measure hand hygiene compliance. Accordingly there is a needto determine whether or not a hand hygiene action occurred when therewas an indication for a hand hygiene action. Hand hygiene actions can besanitizing with a sanitizing product which does not require water forrinsing off or alternatively it can be washing with soap and water.

There are a number of ways to measure compliance—namely directobservation, remote observation, self-reporting and dispenser usage dataor product usage data. Each way has its own benefits and challenges.Specifically direct observation provides specific information on handhygiene behaviors, techniques and indication. However, the labor andresources required to collect such data is intensive. Generally if thistype of data is collected it is only collected for a small sample of thetotal of hand hygiene opportunities and thus has a typically low levelof statistical reliability. The data is also subject to bias from overor under sampling of certain shifts and units. As well, it has beenshown that there are also issues regarding observer reliability andtherefore it is difficult to compare the results from one observer withanother.

In regard to remote observation, such as video, the advantage is that itis less subject to bias and it can operate at any time of day or nightand in any unit. However, such a method of data collection is expensivebecause of the installation and maintenance of the video equipment aswell as the time to review the video, such review is then subject to thesame lack of observer reliability as direct observation. Further, it canbe subject to bias based on the video location. Further, there may beprivacy issues in regard to video locations.

In regard to the self-reporting option, this has the advantage of beinglow cost and it encourages health care workers with respect to handhygiene self-awareness. However, in general this type of data collectionhas poor reliability and most experts in the field consider this methodof little, if any, value.

In typical healthcare environments, hand hygiene liquids are stored anddispensed onto the hands from dispensers. Therefore, there is a directcorrelation between dispenser usage or activations and hand hygieneevents being performed. Dispenser usage data can provide the productvolume used per patient day or the number of times the dispenser wasused per patient day. This has the advantage of being less costly tomonitor and it is not subject to selection bias. Dispenser usageinformation can be collected manually or electronically. Electronicallymonitoring dispenser usage: 1) allows organization-wide trends to betracked over time; 2) can be unobtrusive and designed to take up littleadditional space; 3) can be used across all shifts, twenty-four hours aday, and seven days a week; 4) requires minimal staff training; and 5)can be done in many different healthcare settings.

In the embodiments herein the dispensers are capable of determining whenthey are activated. A plurality of activations within a short period oftime may indicate that one user has activated the dispensers a pluralityof times rather than multiple users activating the dispenser very closetogether. Therefore, a plurality of activations within a predeterminedactivation period may be considered a single dispenser usage event. Forexample, a plurality of activations within a 1 to 4 second time framewill be considered a single dispenser usage event. For hand soaps andhand sanitizers in a healthcare facility, this may be set at 2.5seconds. However, where dispenser usage is being monitored for differenttypes of products in different types of facilities, this may be set fora different activation period. Typically dispensers are calibrated todispense a predetermined amount of liquid per activation. Accordingly,the dispenser activation directly relates to product usage.

FIG. 1 is a diagram showing a wireless information collection system inaccordance with the present invention. System 50 is a dispenser usagemonitoring system that comprises at least one dispenser 52, a wirelessmonitoring network, and a data collation server 58. The dispenser 52comprises a transmitter that wirelessly reports dispenser use to thewireless monitoring network that, in turn, forwards dispensertransmissions to the data collation server 58. The wireless monitoringnetwork is created by at least one hub 54 and at least one gateway 56.

In the wireless system 50 the dispenser 52 is wirelessly connected to ahub 54 and/or a gateway 56. The gateway is connected to a data collationserver 58. Data may be sent from the gateway 56 to the server 58 in aburst by way of a wired network (e.g., the internet) and/or any cellularnetwork such as GSM. Collected data may also be sent to an offsiteserver for data processing.

Each dispenser 52 has a sensor therein and may be capable of storingdata related to up to 100 or more activations. It will be appreciated bythose skilled in the art that 100 activations is by way of example onlyand that typically each dispenser may need to only store data relatingto a few activations. This minimizes the chance of losing data in theevent of queuing for receipt by the hub 54. The data is sent between thedispenser 52 and the hub 54 and between the hub 54 and the gateway 56 inbursts which may be time or memory dependent.

When a dispenser usage event occurs, the dispenser may wait 2.5 seconds,for example, to monitor for repeated dispenser actuations.

Before a dispenser is able to transmit a message it first attachesitself to a hub or gateway device. This is done through a broadcastevent that is replied to by any hubs or gateways within range. The replyincludes the address of the hub or gateway and the current time in UTCformat. This is sometimes referred to as a “handshake.” If anacknowledgement is not received by the dispenser, the dispenser willretry until it receives an acknowledgement from a hub. The dispenser maytransmit connection inquiries and repeat up to 10 times at 2 secondintervals is no hub responds.

The dispenser saves the address of the hub or gateway with the highestreceived signal strength and resets its clock to the received timestamp.

If a broadcast is not successful then the existing time is left as is,but the address for communications is reset to indicate to the dispenserthat no valid radio path exists.

The hubs send the dispenser usage data on through the hub network untilthe data reaches a gateway. Each successive hub in the chainacknowledges receipt of the dispenser usage data from the previous hub.If an acknowledgement is not received by the originating hub, it willretry until successful. The hubs within the transmission distance of thegateway transmit the dispenser usage data to the gateway. When thedispenser usage data is captured by the gateway, it transmits anacknowledgement back to the originating hub.

The gateway 56 collates all of the data it received from the rest of thesystem into transmission “packets” of a predetermined size. These data“packets” are transmitted to the data collation server 58. The data maybe sent to the collation server 58 wirelessly and/or over the internet.When the data “packet” is received or captured by the data collationserver 58 an acknowledgement is sent back to the gateway 56. If anacknowledgement is not received by the gateway 56, it will retry untilsuccessful. This type of system does not require an access point and isoften referred to as an ad-hoc network or a mesh network.

The dispenser connects to a hub in the order of the hub's response to aconnection inquiry by the dispenser. Hubs respond to dispensers afterreceiving the connection inquiry. The hub responses may be delayed basedon the signal strength of the connection inquiry—a longer delay for aweaker signal. The weaker signal may be less reliable as it may indicatea farther distance traveled or a more obstructed transmit path. Forexample the response delay may be computed as:Response Delay=950 milliseconds−(Signal Strength*10)  EQ. 1where the Signal Strength is measured in dB. If signal strength isgreater than 20 dB, a shorter delay may be computed, for example:Response Delay=50 milliseconds+(100−signal strength)  EQ. 2A gateway will acknowledge a hub in the same manner as a hubacknowledges another hub. The dispenser transmitter shuts off when atransmission is acknowledged by the hub. Each transmission comprises anactuation identification number that is sequentially assigned.Therefore, a lost actuation can be identified as missing.

Dispensers are positioned around the facility being monitored. Hubs arepositioned around the facility within range of the dispensers such thateach dispenser is in range of at least one hub. As described above, wheneach dispenser 52 is used, it will transmit its unique identificationcode, date and time to the hub or hubs 54, the hubs 54 in turn transmitthe data to a gateway 56 and then to a server 58. The server 58 may beon site or off site. In a large facility, the system may use a meshnetwork. At each stage of data transmission there will be a “handshake”between the transmitter and receiver whether that be dispenser and hub;hub and hub; hub and gateway; or gateway and server. A handshakeconfirms the data is received and instructs the transmitting device(e.g., dispenser, hub or gateway) to delete the information from thememory.

Accordingly, when designing the system herein for healthcare facilityusage, for example a hospital, there are a number of competinginterests. Specifically the system will require a plurality (e.g.,1,000's) of battery powered activation sensors which need to reliablytransmit usage data wirelessly around a sprawling hospital building. Thesystem must not interfere with medical equipment, comply with regulatoryrequirements and preferably utilize license free radio frequencies.

Hubs may be hard-wired to electrical power since they constantly listenfor dispenser activations and maintain the network communication.Dispenser transmitters can be battery powered to allow more economicalinstallation.

The group monitoring system for dispenser usage data collection mayinclude a plurality of dispensers and a plurality of hubs. Each hub maybe capable of receiving data from up to 10,000 dispensers. The distancebetween each dispenser and its associated hub is typically no greaterthan one mile, and the data is transmitted over a frequency between 850and 950 MHz.

When changes are made to the network and/or messages are not transmittedfrequently, the preferred pathways may be changed and/or becomeunreliable. Therefore, hubs must maintain reliability of connections(i.e. stability) independent of the data flow. To accomplish thisstability, hubs broadcast a “heartbeat.” For example, every 5 minuteseach active hub may broadcast a beacon to find routes to the gateway tomaintain communication connections

An active hub is required, on power up, to establish a route to agateway prior to accepting any messages either from other hubs ordispensers. In order to do this the active hub broadcasts a beacon andthen stores the addresses from the receiving hubs or gateways in a listincluding the number of hops that the active hub has to a gateway. Theactive hub then selects the most direct route to the gateway based onthe number of hops.

FIG. 2 is a diagram showing an active hub 201 in accordance with thepresent invention. The active hub 201 comprises a visible list 203. Thevisible list is a list of all other hubs that are “visible” and theirnumber of hops 207 to a gateway, where the nearest gateway is the onlydestination on the network. Each entry in the visible list 203corresponds to a route and comprises a visible hub ID 205, a hop count207, and a hub age 209.

The visible list may have a fixed number of route entries to reducesystem complexity. For example, the visible list may be fixed at 10entries long. Route entries visible list may be associated with thesmallest hop counts and/or the visible hubs that respond with the leastdelay. The route with the least hops is preferred and should be selectedfirst.

When a hub or gateway broadcast has not been seen for 3 times thebroadcast interval (i.e. 15 minutes) it may be deleted from the visiblelist. The maximum number of hops allowed may be set to 5 in order tominimize the convergence time when a problem (such as a loop) occurs.

Every message forwarded has a “hop count” indicator that is incremented.If the number of hops indicated is above a route threshold, the hub setsthis route via its visible list to infinite (but retains the message).This forces hubs to break a possible loop. When the same transmittedmessage is received back from a listed hub, the number of hopsassociated with the listed hub in the visible list is marked asinfinite.

Hubs will retry to send messages through their preferred route 10 timesbefore switching to the next most suitable route from the visible, toincrease system stability. A running measure of transmission failure maybe kept. For example, a transmission failure will increase (i.e. by 3)the running measure, and a transmission success will decrease (i.e.by 1) the running measure. When the running measure of transmissionfailure reaches a maximum value (i.e. 30) the route is dropped.

On a periodic basis, all hubs with at least one valid route willbroadcast their status, which includes a candidate route indicating anumber of hops. Inactive hubs do not have a valid route, so no periodicbroadcasts are carried out and no hub messages are acknowledged unless ahub is active or live. The active hub 201 will operate to periodicallyprocess 203 data in its visible list 211. For example, every 5 minutesthe active hub 201 will broadcast a beacon 219 comprising an active hubID 221 and a candidate route. A longer broadcast interval may be used tominimize radio traffic.

The candidate route is the minimum number of hops from the receiving hubto the gateway if a first hop is to the active hub 201. Since theminimum hop count from the active hub to the gateway is stored in thevisible list of the active hub, the candidate route is equal to theminimum 223 hop count 207 in the visible list 203 of the active hub 201plus one 225 to account for the hop from the receiving hub to the activehub 201. A hub may only broadcast 229 if the candidate route is lessthan a route threshold 227. For example, routes may be limited to 5 hopsor less.

The hub age 209 of each route entry in the visible list 203 of theactive hub 201 will be periodically incremented 213. When a route entryhas an age that exceeds the age threshold 215, that route will bedeleted 217. For example, the age threshold may be 3 beacon intervals or15 minutes. If a route has not been received in 15 minutes, the routemay be unavailable.

The active hub 201 may receive a response to the beacon 231, and the hubage of the route entry associated with the response 231 may be reset.This broadcast timer is reset, since the route has proven to be valid.

FIG. 3 is a diagram showing a gateway in accordance with the presentinvention. A gateway 301 may broadcast a beacon 303 in the same way asthe active hub 201. The gateway beacon may comprise a gateway ID 305 anda candidate route 307. However, the candidate route 307 of the gateway301 will always be set the same value. The direct route from a receivinghub+ to the gateway is one hop.

FIG. 4 is a diagram showing a receiving hub in accordance with thepresent invention. A receiving hub 401 is a hub that receives a beacon219 from the active hub 201. A hub may operate as an active hub and areceiving hub, in that the active hub may receive a beacon from anotheractive hub.

Upon receipt of the beacon 219 from the active hub 201, the receivinghub 401 may transmit a response 231. This response 231 may comprise theactive hub ID and the receiving hub ID 403. The response may be delayedaccording to the beacon's signal strength measurement as described abovewith reference to EQ. 1 and EQ. 2.

The active hub will transmit route update information after thebroadcast. For example, route update information may be transmitted 3seconds after the broadcast from the active hub. The receiving hub 401may update its visible list 211 according to the route updateinformation. The receiving hub 401 may add a route entry associated withthe active hub ID 205 and the hop count 207 of the broadcasted candidateroute may be saved. The hub age 209 of the route entry associated withthe active hub may be initialized. If the visible list 211 of thereceiving hub 401 already has a route entry associated with the activehub 201, the receiving hub 401 may need to update the hop count 207associated with the active hub if the hop count associated with theactive hub has changed.

FIG. 5 is flow chart showing a method for stabilizing a wireless networkthat operates to monitor dispenser usage in a facility. Networkstabilization enables a higher level of overall system performance andminimizes the number of missed messages from the dispensers.

A hub age of each route entry in a visible list of an active hub isperiodically incremented according to the beacon timer at 501. Theactive hub is a hub that has at least one route entry stored in thevisible list. The route entry must be valid, in that the hop count mustbe less than a route threshold and the hub age must be less than an agethreshold. For example, the route threshold may be set to a maximum of 5hops, and the age threshold may be set to 3 broadcast intervals.Periodically the hub age, of each route entry, may be compared to theage threshold. The route entries, from the visible list, associated witha hub age that is above the age threshold may be removed.

A beacon is periodically broadcasted from the active hub at 503. Thebroadcast interval may be, for example, 5 minutes. The beacon comprisesan active hub ID and a candidate route. The candidate route is theminimum number of hops from a receiving hub to a destination if a firsthop is to the active hub, and the candidate route is equal to one plusthe minimum hop count in the visible list of the active hub.

The destination for all routes is a gateway. The gateway will alsobroadcast a beacon with a candidate route corresponding to 1 hop.

At 505, a beacon is received at a receiving hub. The receiving hubresponds to the beacon at 507. When the response is received by theactive hub, the active hub may reset the hub age of the route entryassociated with the receiving hub.

The active hub will broadcast route updates at 509. A visible list ofthe receiving hub may be updated according to the route updates. If thevisible list of the receiving hub does not comprise a route entryassociated with the active hub a route entry associated with the activehub may be added. If the visible list of the receiving hub does comprisea route entry associated with the active hub and the hop countassociated with the active hub is not equal to the candidate route, thereceiving hub may update the hop count associated with the active hub.

The visible list of the receiving hub and the visible list of the activehub may each comprise a fixed number of route entries. To reduce memoryusage and system complexity, only the route entries associated with thesmallest hop counts may be saved.

New dispensers, hubs and/or gateways may be added to the dispenser usagemonitoring system. As well dispensers, hubs and/or gateways may beremoved from the system. Dynamic system changes are accommodated throughthe protocol described herein. New hubs may be initialized with no validroutes. The visible list of a new hub is populated automatically byprocessing beacons and response. At startup only gateways are ‘live’ or‘active’ to ensure stable startup scenarios.

FIG. 6 is sequence diagram showing a method for stabilizing a wirelessnetwork in accordance with the present invention. This Unified ModelingLanguage (UML) sequence diagram 600 illustrates a network start-upscenario. For illustration of the disclosed embodiment, the networkconsists of a sever 601, a gateway 603, and two hubs—hub 605 and hub607.

The UML sequence 600 shows both the establishing and the maintenance ofthe routes. When the network is initialized, gateway 603 is the onlyactive wireless member. When hub 605 is introduced into the network, hub605 will broadcast a beacon for the first time. The broadcast 609 fromhub 605 is received by gateway 603 and hub 607. Gateway 603 will respondto the broadcast 609. However, hub 607 will not respond to the broadcast609 since it is not yet active. Responses to broadcasts may be delayed.A response delay may be, for example, less than 4 seconds. The protocolfor the broadcast response may comprise a TIME transfer, a ROUTEREQUEST, and a ROUTE RESPONSE.

When hub 607 is introduced into the network, hub 607 will broadcast abeacon for the first time. The broadcast 611 from hub 607 is received byhub 605. However, hub 605 will not respond to broadcast 611 until hub605 has established a route to gateway 603. When hub 607 does notreceive a response from hub 605, hub 607 will rebroadcast its beacon at615. There may be a RETRY DELAY before a hub rebroadcasts. The RETRYDELAY may be, for example, 30 seconds.

The rebroadcast 615 by hub 607 is received by hub 605. Since therebroadcast 615 follows a route update 613 by hub 605, hub 605 willrespond to the rebroadcast 615 from hub 607. A route update 617 by hub607 will follow this affirmative response from hub 605.

A second broadcast beacon 619 is sent by hub 605 after the routemaintenance interval. Broadcasts from hubs continue periodically at arate determined by the route maintenance interval. The route maintenanceinterval may be the same for all hubs and may be set to 5 minutes.

At point 621, hub 605 receives broadcast responses from gateway 603 andhub 607. These broadcast responses may be used to update the routingtable at hub 605 and reset the associated route timers.

When hub 607 is notified, at 623, that the routing table of hub 605 hasbeen updated, the entry associated with hub 605 in the routing table ofhub 607 will be updated. However, this notification 623 may not resetthe route timer in hub 607 associated with hub 605.

Embodiments of the present invention are disclosed herein. However, thedisclosed embodiments are merely exemplary, and it should be understoodthat the invention may be embodied in many various and alternativeforms. The Figures are not to scale and some features may be exaggeratedor minimized to show details of particular elements while relatedelements may have been eliminated to prevent obscuring novel aspects.Therefore, specific structural and functional details disclosed hereinare not to be interpreted as limiting but merely as a basis for theclaims and as a representative basis for teaching one skilled in the artto variously employ the present invention. For purposes of teaching andnot limitation, the illustrated embodiments are directed to a dispenserusage compliance system.

As used herein, the terms “comprises” and “comprising” are to beconstrued as being inclusive and open rather than exclusive.Specifically, when used in this specification including the claims, theterms “comprises” and “comprising” and variations thereof mean that thespecified features, steps or components are included. The terms are notto be interpreted to exclude the presence of other features, steps orcomponents.

What is claimed as the invention is:
 1. A wireless system that operatesto monitor wireless transmissions from one or more dispensers, thesystem comprising: a dispenser that operates to wirelessly communicate ausage event to at least one of a plurality of hubs; a receiving hub, inthe plurality of hubs, that operates to: receive a beacon; transmit aresponse to the beacon; and update a visible list of the receiving hubaccording to the received beacon; and an active hub, in the plurality ofhubs, that operates to periodically: increment a hub age of each routeentry in a visible list of the active hub; and broadcast the beaconcomprising an active hub ID and a candidate route, wherein the candidateroute is the minimum number of hops from the receiving hub to adestination if a first hop is to the active hub, and the candidate routeis equal to one plus the minimum hop count in the visible list of theactive hub, and wherein the receiving hub is operable to update a hopcount associated with the active hub if the hop count associated withthe active hub is not equal to the candidate route.
 2. The system ofclaim 1, wherein the receiving hub operates to add a route entryassociated with the active hub and initialize a hub age of the addedroute entry, if the visible list of the receiving hub does not comprisea route entry associated with the active hub.
 3. The system of claim 1,wherein the active hub comprises at least one route entry stored in thevisible list, the at least one route entry comprises a hop count lessthan a route threshold, and the hub age of the at least one route entryis less than an age threshold.
 4. The system of claim 1, wherein theactive hub is operable to receive the response to the beacon.
 5. Thesystem of claim 4, wherein the active hub is operable to reset the hubage of the route entry associated with the response to the beacon. 6.The system of claim 1, wherein the destination is a gateway.
 7. Thesystem of claim 6, wherein the gateway is operable to broadcast a beaconwith a candidate route corresponding to 1 hop.
 8. The system of claim 1,wherein the visible list of the receiving hub and the visible list ofthe active hub each comprise a fixed number of route entries associatedwith the smallest hop counts.
 9. The system of claim 1, wherein thereceiving hub will not acknowledge the active hub if the active hub isnot in the visible list.
 10. The system of claim 1, wherein the activehub is operable to periodically compare the hub age, of each routeentry, to an age threshold and remove the route entries, from thevisible list, associated with a hub age that is above the age threshold.11. A method for stabilizing a wireless network that operates to monitordispenser usage in a facility, the method comprising: periodicallyincrementing a hub age of each route entry in a visible list of anactive hub in a plurality of hubs; periodically broadcasting a beaconcomprising an active hub ID and a candidate route, wherein the candidateroute is the minimum number of hops from a receiving hub to adestination if a first hop is to the active hub, and the candidate routeis equal to one plus the minimum hop count in the visible list of theactive hub; receiving a beacon at a receiving hub, in the plurality ofhubs; updating a visible list of the receiving hub according to thebeacon; transmitting a response to the beacon; enabling communication toa dispenser that operates to wireless communicate a usage event to atleast one of a plurality of hubs; and updating the hop count associatedwith the active hub if the hop count associated with the active hub isnot equal to the candidate route.
 12. The method of claim 11, whereinthe method comprises adding a route entry associated with the active huband initializing a hub age of the added route entry, if the visible listof the receiving hub does not comprise a route entry associated with theactive hub.
 13. The method of claim 11, wherein the active hub comprisesat least one route entry stored in the visible list, the at least oneroute entry comprises a hop count less than a route threshold, and thehub age of the at least one route entry is less than an age threshold.14. The method of claim 11, wherein method comprises resetting the hubage of the route entry associated with the response to the beacon. 15.The method of claim 11, wherein the destination is a gateway.
 16. Themethod of claim 15, wherein method comprises broadcasting a beacon witha candidate route corresponding to 1 hop from the gateway.
 17. Themethod of claim 11, wherein the visible list of the receiving hub andthe visible list of the active hub each comprise a fixed number of routeentries associated with the smallest hop counts.
 18. The method of claim11, wherein the method comprises periodically comparing the hub age, ofeach route entry, to an age threshold and removing the route entries,from the visible list, associated with a hub age that is above the agethreshold.